On Sept. 20, American Airlines debuted new uniforms for 70,000 frontline employees after three years of development. It was a moment to be celebrated for the carrier, one of the most visible steps toward unifying its workforce following its merger with US Airways.

But then the complaints started.

Within a week of the uniforms’ debut, about 500 flight attendants had reported eye and skin irritation, headaches and a variety of other symptoms they attributed to their new outfits.

What has followed is a medical mystery that is entering its fifth month. American and uniform manufacturer Twin Hill have made repeated assurances that the garments are safe.

Still, the number of flight attendants reporting symptoms they blame on their uniforms continues to rise by about 10 per day and sits at 2,600, according to the Association of Professional Flight Attendants. That’s about 1 out of 10 American flight attendants.

So far, four rounds of testing have been conducted since September and no culprit has been identified.

Shortly before Christmas, the union demanded a recall of all the new uniforms, but American declined.

The two sides are preparing for a new round of joint tests on the uniforms, while some flight attendants have begun contacting lawyers ahead of possible legal challenges. But for now, there’s no clear resolution in sight, or even a hint of what’s making American’s flight attendants sick.

“I love my job. I want to keep doing my job,” said Heather Poole, an American Airlines flight attendant who has chronicled her issues with the uniform to her 100,000 followers on social media. “With what we’re dealing with now, we don’t have time to wait for the union. I don’t have time to wait for American.”

Rashes, headaches and wheezing

Poole said she first noticed something was different after a week of wearing the new uniform, but initially chalked it up to the demands of the job.

“I was super tired. I was flying international and a lot of people get aches,” said Poole, who authored the book Cruising Attitude about life as a flight attendant. “You can always blame it on something else. Who blames it on the uniform?”

But her symptoms continued to get worse and her blood work showed the return of a thyroid condition for which she’d been taking medication.

Now, Poole says her symptoms include coughing, sneezing and trouble breathing. While she can’t prove her uniform is behind the problems, it’s the only thing she can point to.

“To prove you’re being poisoned from a uniform is a little insane,” said Poole, who recently switched to wearing look-alike uniform pieces from a different manufacturer. “All I know is when I put on the uniform I feel bad and I’ve never felt that before.”

Aside from the union, Poole has been one of the only American flight attendants to speak out publicly on the issue so far.

(American Airlines)

(American Airlines)

(American Airlines)

(American Airlines)

(American Airlines)

But behind closed doors and in private Facebook groups, flight attendants have been sharing their stories and pictures of their reactions as the situation continues to escalate.

In a formal grievance filed with the airline, the union’s president, Bob Ross, described a range of symptoms reported by flight attendants, including “endocrine issues, eye swelling, rashes, skin blistering, throat and eye irritation, wheezing, coughing, headaches, vertigo and fatigue.”

In the grievance, Ross requested that American recall all the uniforms, grant requests for sick or personal leave by affected flight attendants, and reimburse them for the costs they’ve incurred.

“These uniforms continue to put our members at risk, forcing them to use sick leave and affecting their overall health,” Ross wrote.

American’s response

American has acknowledged that its flight attendants are suffering from unusual reactions, but it’s repeatedly denied any link to the uniforms.

“Our priority has always been the safety of our team members,” American spokesman Kristen Foster said. “We take their concerns seriously. We’ve been trying to put out alternatives and to communicate clearly with them and [the union].”

The carrier conducted two rounds of testing on the various uniform pieces before the September launch. It also had a group of 500 employees, including 100 flight attendants, wear-test the uniforms ahead of their debut with no reported issues, according to the company.

The new uniforms have been described as a wool-rich blend, while previous American uniforms were made with synthetic materials. Results of the various tests done by American, the union and the uniform manufacturer have not been publicly released.

American Airlines Flight Attendant Diane Huisenga, wearing one of the airline's new uniforms, heads to her flight to Hong Kong at DFW Airport, Tuesday, September 20, 2016. (Brandon Wade/Special Contributor)

(Special Contributor)

American Airlines Customer Service Agent Jim Harrelson poses for a photo, wearing one of the airline's new uniforms, at DFW Airport, Tuesday, September 20, 2016. (Brandon Wade/Special Contributor)

(Special Contributor)

American Airlines Customer Service Agent Yolanda Walter, wearing one of the airline's new uniforms, helps customers at DFW Airport, Tuesday, September 20, 2016. (Brandon Wade/Special Contributor)

(Special Contributor)

American Airlines First Officer Jon Schlegel, wearing one of the airline's new uniforms, heads to his flight to Frankfurt, Germany, at DFW Airport, Tuesday, September 20, 2016. (Brandon Wade/Special Contributor)

(Special Contributor)

After complaints started rolling in, American set up a hotline for affected flight attendants and ordered another round of testing. The airline estimates it has spent $1.2 million on testing so far.

“Nothing in this exhaustive testing has indicated any health risk related from the uniform,” the company’s managing director of labor relations, Cindi Simone, said in a letter to the union this month.

The company said it has received 450 filed reports about the uniform, including 350 from flight attendants. Unions representing other American employee groups, including pilots, have reported some issues, but not nearly to the extent of the flight attendants group.

The company has been working with flight attendants having problems on a case-by-case basis, including allowing them to wear alternative non-wool versions of the uniform, wearing their old uniform or buying similar pieces off the rack.

Uniform manufacturer Twin Hill, a subsidiary of Houston-based Tailor Brands, which owns Men’s Wearhouse, also has spoken out in defense of its products after accusing the union of making “inaccurate and damaging” statements.

The company conducted its own rounds of tests after the controversy started, reporting that the results showed “there are no restricted chemicals in the garments and the chemicals that are present are well within acceptable standards for the clothing industry.”

Next steps

In its formal grievance, the union called on American to recall the uniforms and accused the airline of violating contract provisions governing “the safety, health and security of flight attendants.”

But American denied the recall request and the grievance, pointing to the results from its multiple tests and its continued efforts to resolve the issue with the union.

American’s denial of the grievance means the case could head next to arbitration, where the two sides would present arguments and evidence to a third party, which would decide whether American’s actions violate the flight attendants’ contract.

Flight attendants have also been reaching out to lawyers about possible legal action, which could range from workers’ compensation claims to a product liability challenge against the uniform manufacturer.

But proving legal liability would likely be challenging and require providing a scientific explanation of what exactly is making the flight attendants sick.

“I think the testing is going to be critical to understanding this situation,” said Scott Poynter, an Arkansas attorney with the Poynter Law Group who is working with several American flight attendants.

Poynter previously brought a suit on behalf of 164 Alaska Airlines flight attendants against Twin Hill over similar complaints of adverse reactions to that carrier’s uniforms.

As in American’s case, the chemicals in the Alaska uniforms tested within acceptable standards. But experts testifying on behalf of the flight attendants put forward a theory that an unexpected interaction between those various chemicals was to blame for the issues.

A California court rejected that argument and ruled in favor of Twin Hill in September.

The next step in American’s case will likely include another round of testing, this time conducted jointly by the union and the carrier. The two sides are working to organize that test, which would involve representatives from both groups selecting pieces to be analyzed from Twin Hill’s warehouse.

Initially scheduled for November, that effort has been repeatedly pushed back as the union and American negotiate testing protocols.

“We just want to make sure it’s done in a way ... that gives us the information we need to find out what the problem is,” the union’s spokesman Shane Staples said.